A tendency to a greater use of ground waters for water supply is currently observed. This is explained by the well known fact that ground waters as a water source have a number of advantages compared to the surface waters. Natural resources are indicators of renewal of ground waters reflecting their main peculiarity as a renewed resource. The long-term value of ground water source minus evaporation is equal to the underground sink, therefore in the regional estimates, natural resources of ground waters are frequently expressed by the annual mean or minimal absolute values of underground sink in liters per second from 1nbsp;km2nbsp;. The main methods of regional estimates of natural resources, their advantages and restrictions method of genetic division of rivers hydrographs over a long-term period, estimates of the variations in the low runoff between hydrometric lines, hydrodynamic method of calculation of flow discharge including modeling, method of water balance of source regions or reload of ground waters, estimate of infiltration source of ground waters based on the regime of their levels are described in this presentation. The choice of the specific method for calculating water resources depends on the objectives, goals, and scale of investigation and on the hydrological, hydrogeological, and anthropogenic conditions of the estimated territory.